Medicament inhaler devices are well known. They come in many different forms and may be used in the treatment of a number of ailments.
Inhalers are typically used by patients over prolonged periods without supervision. In particular for conditions like asthma, it is important for a user to have a reliable record of the level of medicament remaining in an inhaler so as to ensure that they have a sufficient supply at all times. For this reason, it is increasingly common for inhalers to be provided with dose counters to keep track of the number of doses expelled from, or remaining in, an inhaler.
The present invention provides a dose counter mechanism, preferably for use with a Metered Dose Inhaler (MDI). Metered Dose Inhalers are typically provided with a pressurised canister of medicament for delivery. The MDI canister has a valve stem which, on actuation, will release a predetermined dose of medicament. Actuation of an MDI inhaler typically involves restraining the valve stem in a housing and applying pressure to the opposite end of the MDI canister to force the valve stem to move into the canister and administer a dose. The valve stem then springs back into position once a said force is removed from the canister.
Counters are useful in a wide variety of applications, and are especially important in the field of medical dispensers e.g. a metered-dose inhaler (MDI) where an accurate determination of the number of doses of medicament remaining in a medicament container might otherwise be difficult to obtain.
WO2006/062448 discloses a dose counter comprising a tape provided with numbers which is advanced on each actuation of the inhaler. The dose counter is mounted for movement with the canister.
WO99/36115 discloses an alternative dose counter which comprises a rotatable disc to display the remaining doses. The dose counter of WO 99/36115 is mounted in the housing of an MDI inhaler and comprises a complex gear linkage, including a worm gear, to translate linear motion of the canister into rotational motion of the count disc.
In particular, and as evident from the prior knowledge and art, there are difficulties in providing simplistic dose counters or dose counting assemblies that reliably “count” the release of medicament doses from the medicament containers/inhalers, specifically, MDIs.
The dose counter of the present invention provides a simple mechanical means for counting the number of actuations of a canister by translating this linear movement of the canister into rotational movement in a single rotational direction.